1. Field of the Invention
This invention relates to novel cycloalkylsulfonates which are useful in preparing polymers. The polymers are particularly useful in the photographic arts. In one of its aspects, this invention relates to the use of the compounds to prepare polymers which are incorporated into radiation-sensitive elements. In another of its aspects, this invention relates to the preparation of such compounds.
2. Description Relative to the Prior Art
The polymerization of aromatic sulfonates with other dicarboxylic acids and diols to form ionic polyesters is known in the art. For instance, U.S. Pat. No. 4,167,395 issued Sept. 11, 1979, discloses a water-soluble polyester containing recurring units derived from dimethyl 5-(p-sodiosulfophenoxy)isophthalate. However, when polyesters containing this solubilizing aromatic sulfonate compound are brought into contact with ordinary tap water, they exhibit scumming due to an exchange of sodium ions with the mono-, di- and trivalent ions in tap water. Therefore, the use of these aromatic sulfonate polyesters which requires contact with water, also requires the use of carefully distilled or deionized water and an environment free from the exchanging anions causing the undesirable scumming.
Problems have also been encountered with alkyl sulfonates, which are generally thermally unstable at the temperatures needed to prepare polyesters by standard melt polymerization techniques.
U.S. Pat. No. 3,682,866, issued Aug. 8, 1972, discloses that cyclohexanesulfonates, such as sodium 1,3-dicarboxycyclohexane-5-sulfonic acid, is prepared by hydrogenating an aqueous solution of the corresponding aromatic sulfonate in the presence of a palladized carbon catalyst. However, attempts to prepare the dimethyl ester of this cycloalkyl compound in accordance with the disclosed procedure have not resulted in successfully polymerizable compounds. During the aqueous hydrogenation procedure the ester function is hydrolyzed to a great extent to the free diacid, as well as other compounds, which composition is polymerizable only with great difficulty due to its high melting point. The "polymers" obtained from these compounds are very low in viscosity and are contaminated with considerable amounts of unpolymerized free acid. Thus, they are useless for most purposes for which ionic polyesters are sought. Further, the attempted condensation polymerization of these diacids releases water which is extremely difficult to remove completely from a polymer melt. Volatile alcohols which are easily removed are given off during the condensation of a lower alkyl diester.
It is surprising that 1,3-dicarboxycyclohexane-5-sulfonate esters, even if obtainable in unhydrolyzed, easily polymerizable form, improve the solubility of a polyester to a significantly greater degree than the use of aromatic sulfonate compounds. The sulfonate group of a 1,3-dicarboxycyclohexane-5-sulfonate is relatively close to the carbon backbone, and the resulting steric hindrance is expected to reduce the effectiveness of the sulfonate moiety as a solubilizing group.
It would be highly desirable to obtain cycloalkylsulfonates in unhydrolyzed, easily polymerizable form, which are thermally stable at temperatures required by standard melt polymerization techniques. A method of making these compounds in good yield is also desirable. Still further, it would be desirable to obtain condensation polymers which would not tend to exchange ions with other cations in surrounding aqueous environments. Such condensation polymers exhibiting improved salt tolerance would be useful in the presence of ordinary tap water, rather than requiring the use of expensive distilled or deionized water to avoid scumming and insolubilization of the polymer.